The H5N1 influenza has proven extraordinarily deadly. More
than 50 percent of the 500 cases that have been documented since the virus
first emerged in 1997 have been fatal. Thus, H5N1 is viewed as a serious threat
to world public health. A major difficulty in developing antibodies to combat
this virus is that ten different antigenic types have evolved since the virus
first emerged. But now a team of researchers has produced a so-called
cross-reactive antibody that can bind to nine of the ten H5N1 groups. They
showed further that it could protect mice from infection, and that it could be
used to treat established infections in the mice. The research is published in
the March Journal of Virology.

The investigators approached the problem of finding
cross-reactive antibodies by hypothesizing that H5N1 survivors might sometimes
make small amounts of such versatile antibodies, thus accounting for their
survival, says co-principal investigator John J. Skehel of the National
Institute for Medical Research, London, UK. They then found such antibodies in
an H5N1 survivor, which they expressed in insect cells, to produce sufficient
quantities of antibody to conduct their medical experiments.

Skehel sees an eventual cross-reactive antibody product
being used in conjunction with anti-Neuraminidase drugs as a more effective
treatment for H5N1 than either alone, partly because the dual treatment could
prevent development of resistance to the anti-Neuraminidase drugs, which is a
problem when they are used as monotherapies.

An additional finding is that the cross-reactive antibody
interacts with the virus’ hemagglutinin, a protein that is responsible for
binding the virus to the cell that it is invading. A clear understanding of
this interaction might help researchers develop vaccines that would induce
cross-reactive antibodies, thus overcoming the current need to make new
influenza vaccines each year,” says Skehel.